Aikido pins are not very secure from the physical/mechanical standpoint. That is to say, using only your body to apply an Aikido style pin is not very effective. However if you add the addition of a weapon, the pins have a very high level of security.

Aikido pins are of the type where one can easily apply the pin and still hold a weapon. Further the pins found in Aikido do a very good job of keeping the person you are pinning from using any potential weapons they may have. Further, Aikido pins are done in a way that allows nage to leave the pin rather quickly. Which is of paramount importance if one is facing multiple attackers.

While Aikido pins do lack the physical control found in many unarmed grappling styles, they do offer many advantages that wouldn't be found in their unarmed grappling counterpart: ability to control and use your weapon, ability to keep the person you are pinning from using their weapons while they are in your pin, and ease of escape for nage if something changes.